Cupola furnace



Oct. 29, 1929. F. A. STEVENSON CUPOLA FURNACE Filed June 29,4 1928 4 Sheets-Sheet 1 ATTOAA/EY Oct. 29, 1929, F.'A. STEVENSON CUPQLA FURNACE Filed June 29; 1928 4 Sheets-Sheet 2 F re derz'rk 4. Stevenso Arron/var Patented Oct. 29, 1929 UNITED STATES PATENT OFFECE FREDERICK A. STEVENSON, OF NEW YORK, N. Y., ASSIGNOR TO ECONOMY METAL PRODUCTS CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK CUPOLA FURNACE Application filed .Tune 29,

This invention relates to cupola furnaces for use in the smelting and reduction of ores generally, and contemplates a variation of the general design of furnace shown in my sco-pending application, Serial No. 252,506,

filed February 7, 1928.

One of the objects of the present invention is the provision of a cupola of novel design and construction which will effect great economy in fuel.

Another object of the invention is the provision of a cupola wherein the gas producer effect is reduced beyond that generally in existence in connection with the operation of l the usual cupola.

A further object of the invention is the provision of a hot blast cupola in which the air is pre-heated in a zone above the melting zone whereby to reduce the temperature in the furnace above said melting zone to prevent the absorption of carbon by the CO to. reduce the gas producer effect of the cupola.

A still further object of the invention is $5 the provision of a. cupola the shaft of which is in reality divided into three separate and distinct zones of different temperatures; the upper zone being a cool zone, the middle zone being a preheating zone wherein the fuel and ore are pre-hea-ted, and the third zone is the melting zone.

Another object of the invention is the provision of a cupola having means for reducing the temperature in the shaft of the cupola above the pre-heating zone whereby to retain the fuel beds thereinat a cooler temperature, more particularly a temperature such that the major portion and in fact the maximum number of the heat units of the fuel will be preserved or retained in the fuel prior to the delivery thereof to the pie-heating zone of the cupola.

' The invention contemplates the substitution of a metallic lining or liner for a portion of the usual refractory lining, the metallic liner serving to define in conjunction with the outer casing'or sheathing of the furnace, a heating chamber for air which will absorb or take from said metallic lining the heat thereof, thereby permitting said 1928. Serial No. 289,100.

metallic lining to absorb more heat from the shaft of the furnace and thus reduce the temperature in the shaft above the pre-heating and melting zones of'the furnace to retain the fuel beds in this portion of the furnace at a temperature much below that normally found in the usual cupola of today, such temperature being insuflicient to destroy the heat units in the fuel in this particular zone.

The usual cupola, as is well known, has a gas producer effect, and the fuel layers in the shaftof the cupola are subjected. to intense heat from the moment they are introduced into the upper section of the cupola, which temperature gradually increases until the fuel beds reach the melting zone. The operation of such a furnace necessarily results in the destruction of heat units in the fuel beds above the melting zone, and such heat units go off as waste and are lost prior to the utilization of the fuel in the pre-heating or melting zone.

Fundamentally, it is the aim of the present invention to conserve the heat units in the fuel beds or layers until they reach the melting zone of the furnace, and it has been found that by reducing the temperature in the shaft of the cupola above the melting zone, such heat units are preserved until they reach the pre-heating zone where they are pro-heated prior to reaching the melting zone. It has been found that when the temperature of the combustion gases in the furnace is high, the coke or other fuel charge required for the efiicient operation of the furnace, is proportionately high, andit has further been found that when the temperature of the combustion gases in the furnace shaft above the melting and pre-heating zones is reduced, the fuel charge necessary for the same eflicient operation of the furnace is proportionately reduced. This, it is believed, is due to the particular construction and operation of the furnace of the present invention, which is now to be described.

In addition to the objects specified above, various other objects and advantages of the invention will be apparent to those skilled in the art from the following description, taken with the accompanying drawings, in which:

Figure 1 is sectional view through the upper portion of the cupola of the present invention;

Fig. 2' is a sectional view through the cupola taken on the line 2-2 of Fig. 1;

Fig. 3 is a sectional view through a portion of the cupola showing the means for retaining the superposed rings in alined relation, the view being taken on the line 3-8 of Fig. 4;

Fig. 4 is an enlarged detail view taken on the line 44 of Fig. 1;

Fig. 5 is a sectional view through one of therings showing the reinforcing ribs thereon;

Fig. 6 is a sectional. view of a modified form of cupola;

Fig. 7 is a sectional view of the cupola shown in Fig. 6, taken on the line 11-11 of said figure;

Fig. 8 is an enlarged detail sectional view showing the securing means for the ring sec tions shown in Figs. 6 and 7, the view being taken on the line 12-12 of Fig. 7;

Fig. 9 is a sectional view taken on the line 1313 of Fig. 8;

Figs. 10 and 11 are sectional views of rings taken on the lines 14-14, 15, of Fig. 3;

Fig. 12 is a detail sectional view of one of the guides used with the furnace shown in F ig. 1; and

Fig. 13 is a detail sectional view of one of the retainers associated with the guides shown in Fig. 12.

Referring now more particularly to the drawings, and specifically to Fig. 1, 2 designates the outer casing or sheathing of a cupola furnace which is mounted on a suitable base .(not shown) and which furnace is provided with charging doors 6 and a chute 8 for an obvious purpose; the interior of the casing being provided at its lower portion with a refractory lining 10 which extends upwardly above the melting zone of the cupola.

In general the invention contemplates the provision of an air heating chamber arranged above the melting Zone and the combustion zone of the furnace, said air heating chamber being so formed and arranged as to take heat from the shaft of the furnace whereby to reduce the temperature in the shaft above the combustion zone to thereby preserve the heat units in the fuel in the adjacent portion of the furnace shaft. To that end, I substitute for a portion of the refractory lining, which is usually continuous from the base to the top of the furnace, a metallic lining indicated generally at A in Fig. 1, said metallic lining extending to the upper end of the furnace shaft and forming the inner wall of an air heating chamber, the outer wall of which is designated as B, the latter being arranged between the inner liner A and the outer casing 2 and defining the chamber C which receives air from an intake 12 arranged at the lower portion of the chamber, said air to be heated in said chamber and delivered in a highly heated condition to a downcomer 14 and then to the wind box and tuyeres (not shown )of the furnace, which latter are arranged below the metallic liner in a manner shown in my prior application heretofore identified.

From the description just above, it will be apparent that the air injected into the heating chamber will absorb heat from the inner liner A thus permitting said liner to take heat from the products of combustion in the furnace shaft adjacent said liner, thereby lowering the temperature in the adjacent shaft Zone and preventing the loss of a large number of heat units in the fuel.

Referring now to the particular details of construction, in Fig. 1 it can be seen that the outer casing 2 is preferably formed of sections 16, 18 and 20, the section 16 having an annular supporting ring 22 riveted thereto as at 24. The ring 22 serves to support the liner A in a manner presently to be described. The liner A is preferably formed of metal of such character as to withstand the heat to which it is subjected without cracking or breaking, and in the form of the invention illustrated in Figs. 1 and 2, the liner preferably is formed of a plurality of superposed rings 26, 28, and 32, the cross-sectional construction of which is shown in Fig. 5. The rings are provided with upper and lower supporting flanges 34 and 36 respectively, the upper flanges each being provided with an annular recess 38 which accommodates an alining rib 40 formed on the lower flange of a superposed ring; in other words, each ring is provided with a recess in its upper flange and a depending rib on its lower flange. In practice, it may be desirable to form the supporting ring 22 of a plurality of united or connected sections, as fully disclosed in my copending application aforesaid, but this is optional, as obviously, the ring may be cast in one piece and the same supports the liner in the usual way; the lower ring 26 seating on a reduced portion 42 of the ring 22 whereby it is centered, with the centering rib 40 positioned in a channel or recess 43 formed in said reduced portion. If desired, or to reduce the cost of manufacture, the ring 22 need not be provided with the recess 43, and the lower edge of the rin 22 may be devoid of the centering rib. as will be apparent, it having been found that the ring 26 may be accurately centered merely by being seated on the reduced portion 42, which, in effect, is an annular channel or recess. The remaining rings 28, 30 and 32 are superposed each upon the other, with the ring 28 in superposed relation to the ring 26, with the ribs 40 of said rings eX-- tended into the recesses 38 whereby to aline the rings in an obvious manner.

as before mentioned, the invention contemplates the provision of a metallic inner lining for a portion of the furnace shaft, and in the present instance, the liner is formed of superposed rings. These rings may be continuous and of one piece, or they may each be formed of a plurality of segments, as illustrated in Figs. 1 to 5 inclusive. Referring now to this segmental type of ring, the same comprises a plurality of arcuate segments 44 which, when asembled, form the rings 26 .to 32 inclusive. Each of these segments is provided with external concentrically arranged ribs 46 to define heat radiating mediums, as well as to furnishadequate reinforcements for said segments. The side edges of the segments are each provided with an outwardly extending flange of arcuate form; adjacent or abutting flanges serving to provide and define an arcuate bead 48, and adjacent segments are preferably united or connected by a tongue and groove construction, as shown at 50. To effect this tongue and groove connection, the side edges of the segments are formed with ribs and depressions respectively, whereby when the segments are assembled, as shown in Fig. 4, the rib of one section will be arranged in the groove of the side edge of the next adjacent segment to unite the adjacent segments and to define the arcuate bead 48 heretofore mentioned. Because of the fact that the inner surface of the rings is subject to greater expansion than the outer surface, due to the heat of the furnace shaft, the side edges are bevelled as at 52 which provides a slight space between adjacent segments at the inner surfaces thereof to permit necessary expansion of the segments without distortion which might occur were they closely interfitted' and engaged.

The heating chamber has been described as being defined by theliner'A and the wall B. The latter is arranged intermediate the outer casing and the liner A, and comprises a metallic sheet. 54 of substantially circular crosssection which is arranged completely around the liner A and extends from the horizontal leg 56 of the angle 22 upwardly to a sealing plate 58 mounted by an angle 60 secured to the casing section 20 and by the upper edge of the uppermost ring 32; the latter supporting a false ring 62 which extends to a closing plate 64 at the extreme upper edge of the shaft. It will be clear from the disclosure in Fig. 1 that the sealing plate 58 is firmly retained by means of the upper ring 32 and the false ring 62 as well as by the angle 60 to which said sealin plate 58 may be connected.

Intermediatethe upper and lower ends of the Wall E or sheet 54 is a spacer 66 supported by the angles 68 secured to the casingA and the sheet 54 for an obvious purpose. The sheet 54 really provides two chambers, viz: the heating chamber and an exterior chamber 70 therearound which aids in preventing loss of heat units in the heated air in the chamber C as will beapparent. The intake 12 directs air into this chamber 70 and it passes through the apertures 72 formed in the sheet 54 into the heating chamber at the lower end thereof to be heated in said chamber, and-said air then passes upwardly through the heating chamber in close contact with the outer surface of the liner A and thereby is intensely heated and is then passed out through apertures 74 formed in the upper end of the sheet 54 into the upper end of the down-comer 14 from whence it is delivered into the tuyeres. To permit air to pass from the lower portion of chamber 70 to the upper portion, above spacer 66, suitable apertures may be formed in said spacer, as will be apparent.

It is necessary, of course, to provide means for maintaining the rings 26 to 32 inclusive and the segments forming the same in as sembled relation, and to that end I have provided a plurality of guides 76 which are secured to the inner surface of the sheet 54. The guide-s are arranged in spaced relation around the sheet 54 and are preferably of the form shown in Fig. 4. Each of said guides comprises an attaching portion 78 by which said guides may be secured to the sheet and spaced ribs 80 defining a channel 82 there between, in which is positioned a retainer 84 of the form shown clearly in said Fig. 4. The guides are provided with bases 86 which rest upon the horizontal leg 56 of the angle 22 and are secured thereto by suitable fasteners 88.

The retainer is preferably a casting having a main body portion 90 which is arranged between the ribs 80, and a head portion 92 having a continuous recess therein which is complemental to the before-mentioned bead 48, and which is adapted to engage said bead as shown in Fig. 4. The guides 76 are provided with spaced bosses 94 which extend through the sheet 54 and said bosses are substantially cylindrical in shape and have positioned therein a coil spring 96 which bears against the rear of the body portion 90 of the retainer to force the same against the bead 48. For retaining the springs in engagement with the retainer, the bosses are each provided with a cap plate 98 secured by bolts 100 to the bosses. The cap plates 98 are each provided with an opening 102 for the purpose of admitting air from the outer chamber 70 into said bosses to maintain the retainer in a comparatively cool condition, the retainer being provided with communicating horizontally arranged bores 104.

Referring now to the type of furnace disclosed in Figs. 6 to 10 inclusive, it can be seen that the furnace shown in these figures is provided with an outer casing 146 having a refractory lining 148 in the lower portion thereof; this being identical with the disclosure in Fig. 1. Positioned on the upper surface of the refractory lining 148 is a centering ring 150 having an inner annular recess 152 the ring supporting the metallic lining or liner indicated generally at 154. The metallic lining 15 1 is spaced from the outer casing 146 and is provided with an external flange 156 which seats on the ring 150, as clearly shown in Fig. 6. This lining 154 extends to a point adjacent the upper portion of the furnace and is provided with an external flange 158 upon which is seated a continuous false ring 160 having the supporting flanges 162 and 164. The usual charging doors and chutes are provided, as clearly indicated in this figure. A sealing plate 166 is provided which is supported on an angle 168 secured to the outer casing 146, and said sealing ring extends to and is supported between the flanges 158 and 162 heretofore mentioned. In the drawings, only one false ring is shown, but it is obvious that within the spirit and scope of the invention, a plurality of false rings may be employed, if desired. The construction just generally stated provides an air heating chamber which is designated generally at 168 and the same is adapted to receive air through an intake 170. As shown. clearly in Fig. 7 in conjunction with this modification, an air distributor 172 is provided which is bolted or otherwise secured around the outer casing 1416 adjacent the bottom of the liner 154-, This air distributor is not continuous around the entire outer casing but terminates at points opposite the air intake providing oppositely extending air delivery means for admitting air into the heating chamber 168. The outer casing 146 is provided with a plurality of openings 17 1 through which the air in the distributor passes from said distributor 172 to the heating chamber.

The metallic lining or liner 1541- is formed of a plurality of segments, and in the drawings, particularly Fig. 13, the lining is shown as formed of three s *etions, 181, 186 and 188, which segments are arcuate and each thereof is provided with continuous vertical ribs 190 and with side flanges 192, which latter, when the sections are assembled, are arranged adjacent each other as clearly shown in Figs. 7 and 9.

It has been found that the metallic liner will expand and contract due to the heat of the furnace, and therefore it is desirable to providefor such expansion and contraction to prevent cracking or fracturing of the liner, and to that end, the adjacent side flanges 192 are, when assembled, arranged in spaced relation, as more specifically shown in .9. One of the side flanges 192 is provided with an extended rib 1941 which is arranged to overlap the inner surface of the next adjacent segment in order to seal the joint be.- tween adjacent segments when the latter are either in expanded or contracted position.

For positioning the assembled segments and for retaining them in position, a plurality of vertically arranged castings 196 are provided which comprise a head portion 198 provided with a vertical slot 200 into which the side flanges 192 extend, and an attaching base 202 by which the castings are secured to the outer casing 146 by means of rivets 204 or the like. For preventing the escape of gases from within the shaft of the furnace between the side flanges 192 and for preventing admission of air into the furnace shaft, a sealing medium 206 is provided which may be of asbestos or the like and which comprises a continuous strip extending from the top to the bottom of the segments across their meeting edges. The sealing medium 206 is preferably retained in engagement across the meeting edges of the side flanges 192 by means of a backing strip 208 which may be of metal or any other suitable or desired material, which is retained in position by means of the springs 210 arranged in openings 211 formed in the head 198. For retaining the sprmgs 1n positlon, screw plugs 212 are provided which extend through bosses. 213 formed with the head 198 and extending through the outer casing. The castings are provided with upper and lower attaching portions 215 and 217 respectively, the former being secured to the sealing plate 166 by means of bolts 219, and the latter (217), being secured to the centering plate 150 by means of bolts 221. The castings 196 serve to divide the heating chamber 168 into a plurality of sections, three in the present instance, desig nated as 176, 178 and 180, into which the air from the distributor 172 passes through the apertures 17 1.

In order that the air from the distributor may be uniformly and intensely heated, it has been found desirable to provide a means whereby the air will be directed to the liner and the ribs 190, and to that end, each section 176, 178 and 180 is provided with a de flector or apron 17 7 which is secured to the outer casing 1 16 and extends to the ribs 190, as shown clearly in Fig. 6; the apron serving as a baffle to direct the air to the liner where it can be heated. For the purpose of effecting a slight circulation of air through the heating chamber, to prevent any possibility of the air therein becoming stagnant, apertures 179 are formed inthe aprons, as

clearly shown in Fig. 6. It has been found advisable to provide these apertures in view of thefact that the incoming air is directed to the liner 154 by the aprons and the air travels upwardly adjacent the liner and the ribs thereon. The air being intensely heated in the sections of the heating chamber is led from these sections to the tuyeres of the furnace by means of the conduits 182, only one of which is shown inFig. 6, but it will be apparent that each section of the heating chamher is provided with a conduit which takes the air from its respective section to the tuyeres. As a modification, itis here stated that within the spirit and scope of the present invention, I can employ a collector around the upper portion of the heating chamber into which the air from the several sections of the heating chamber is directed, and provide only one conduit leading to the tuyeres.

Each segment forming the metallic lining is provided with external ribs 190, the particular construction of which is shown clearly in Figs. 10 and 11. Referring to these figures, it can be seen that the ribs are not continuous from the upper to the lower flanges of the segments, but are reduced in width at their ends, and each rib is apertured. The tops of ribs shown in Figs. 10 and 11 alternate on the segments, and the rib in Fig. 10 has been designated specifically at 216, the same comprising a central portion 218 provided with an aperture 220 which is arranged substantially midway between the ends of the segments, and the ends of said ribs 216 taper gradually from the central portion 218 to the ends, as shown at 222. The rib shown in Fig. 11 has been designated specifically as 224 and is provided with apertures 226 arranged adjacent the upper and lower ends of the rib; the rib 224 being of uniform width almost from end to end thereof and sharply reduced at its upper and lower ends as shown The ribs are provided in order that as large a radiating surface as possible may be present for the air to be heated, and the specific design of rib shown in both Figs. 10 and 11 has been adopted for the purpose of permitting expansion of the liner, as will be obvious. The rib itself does not merge with the upper and lower flanges of the liner in order that no strains from the rib will be transmitted to said upper and lower flanges. It will also be apparent that in addition to providing a large radiating surface for the liner, the ribs thereon serve as reinforcements for said liner. The ribs 220 and 226 formed in the ribs shown in Figs. 10 and 11 respectively, are provided for the purpose of permitting expansions of the ribs without subjecting them to excessive strains such as might fracture or crack said ribs.

From the above description, it is believed that the operation of the present invention will be fully apparent to those skilled in the art, and heretofore, in this description, brief rsums of the operation have been recited. It is desired to state in addition, however, that when air is admitted to the intakes shown in the several views, it passes into the heating chamber where it is intensely heated by absorbing heat from the inner liner and the air will be directed from the heating chamber into the down-comer and then to the tuyeres where it is injected into the melting zone of the furnace. Further, and as before-mentioned, the provision or substitution of the metallic liningwithin the furnace for a portion of the usual refractory lining, permits and effects the reduction in temperature in the furnace shaft above the melting and combustion zones, thereby reducing the gas producer effect of the entire furnace and a consequent preservation of the heating units in the fuel adjacent the metallic liner until such fuel reaches the combustion zone where it is pre-heated prior to its admission to the melting zone, therefore afiording a greater ratio of fuel than has heretofore beenknown.

In connection with the type of furnace disclosed in Figs. 1 and 2, the intake 12 is shown as at the lower portion of the heating chamber but this is merely by way of example, and it is to be understood that within the spirit and scope of the present invention, the intake 12 may be positioned at the upper portion of the heating chamber and the downcomer 14 may receive air which has been heated in said chamber from the lower portion of said chamber; in other words, the positions of the intake 12 and the outlet from the heating chamber into the downcomer may be reversed whereby the cold air initially admitted into the heating chamber may receive heat from the upper portion of the furnace shaft and become gradually heated in passing from the upper portion of the heating chamber down to the lower portion thereof where said cool air successively receives increased heat durin its downward passage and thereby being injected into the downcomer in a very highly heated state, and in fact at a temperature which is above the temperature of the air which is admitted through the intake 12 positioned at the lower portion of the heating chamber.

Attention is directed to applicants construction of furnace in that there have been provided three distinct zones in the shaft of the furnace; viz, the cool zone in the upper portion of the furnace shaft and adjacent the metallic liner, the pre-heating zone just beneath the cool zone,-and third, the melting zone itself, which of course is adjacent the tuyeres. i

The drawings herein disclose several modifications of the device, but it is to be under stood that the drawings are for illustrative purposes only'and that various changes in the form and proportions of the device may be made within the scope of the appended claims without departing from the spirit of the invention.

l/Vhat is claimed is:

1. In a cupolafurnace having a refractory lining at the lower end thereof, a metallic member forming a part of thelining of the furnace and formed of a plurality of segments, an outer sheathing for the furnace arranged in spaced relation-to the metallic lining to provide an air heating chamber, and means engaging the edges of adjacent lining segments to retain the latter in position and to permit expansion and contraction thereof.

2. In a cupola furnace having a refractory lining at the lower end thereof, ametallic member supported by said refractory lining and forming a part of the furnace lining, an outer sheathing for the furnace, a metallic wall intermediate the outer sheathing and metallic lining and defining with said metallic lining a heating chamber, and retaining members supported by said wall and engaging the metallic lining to position the latter.

A cupola furnace comprising a refractory lining, a segmental metallic liner mounted thereon, an outer sheathing defining with the metallic liner an air heating chamher, an air intake leading into the heating chamber at the lower end thereof, an air outlet leading from the heating chamber adjacent the upper end thereof, and means engaging the segments of the inner liner for retaining the latter in assembled position and for permitting expansion and contraction thereof.

4. A cupola furnace having a lining formed in part of refractory material and in part of metallic segments interfittingly connected together, an outer sheathing for the furnace, a metallic wall intermediate the outer sheathing and metallic lining, apertured bosses secured to said metallic wall and retainers resiliently mounted in said bosses and normally urged to contact with abutting edges of adjacent metallic segments.

5. A cupola furnace having a lining formed in part of abutting metallic segments, an outer sheathing for the furnace providing an air receiving chamber, a metallic wall interposed between the sheathing and metallic segments and dividing the air receiving chamber into a hot air chamber and a cooler air chamber. and means supported by said metallic wall for engaging the abutting edges of the metallic segments for retaining them in desired position and to permit expansion and contraction thereof.

6. A cupola furnace having a lining formed in part of metal of such character as to absorb heat units from the furnace shaft, an outer sheathing spaced from the metal lining and defining with the latter an air receiving chamber, means interposed between the metal lining and outer sheathing for directing atmospheric air in close proximity to the metal lining whereby it takes heat therefrom, and means for directing the heated air from the air receiving chamber.

7. A cupola furnace having a portion of the lining thereof formed of metallic segments to define the inner wall of an air heatin chamber, the side edges of said segments being arranged adjacent each other and being so formed as to permit unresisted individual expansion and contraction, and means engaging the side edges of adjacent segments for retaining said segments in their assembled relation.

8. In a cupola furnace, a shaft having an outer sheathing, a refractory liner in the lower end of the shaft, and a metallic liner forming the upper end of the shaft, said liner defining with the outer sheathing an air heating chamber and comprising superposed rings formed of segments, the side edges of which are arranged in substantial abutting relation and being so formed as to permit individual expansion and contraction of said segments, means engaging the side edges of the segments for retaining the latter in assembled position, and means associated with said retaining means for sealing the adjacent side edges of said segments against leakage from the furnace shaft.

9. In a cupola furnace, an outer sheathing, a refractory lining at the lower end of the furnace shaft and extending above the melting zone of said shaft, a metallic member formingthe remainder of the furnace lining and extending upwardly adjacent the upper end. of the furnace shaft and defining with the outer sheathing a chamber for receiving atmospheric air to be heated by said metallic member, whereby to take heat from the shaft adjacent said metallic member, said metallic member comprising a plurality'of superposed circular elements each formed of arcuate segments, the side edges of which are so arranged in interfitted relation as to permit expansion of the individual segments under the influence of heat, a partition intermediate the sheathing and metallic member for confining air in close proximity to said metallic member to be heated thereby, guides secured to the partition, retainers in said guides and extending substantially the full length of the metallic member and engaging the adjacent side edges of the segments thereof to retain the circular elements in assembled relation, and means urging the retainers into engage ment with the segments.

10. In. a cupola furnace, an outer sheathing, a metallic member forming the upper portion of the liner thereof and comprising a plurality of segments having substantially abutting side edges, said. metallic member being spaced from the sheathing to define a chamber for receiving atmospheric air, and means for retaining the segments in assembled position comprising guides engaging the adjacent side edges of liner segments and adapted to permit expansion and contraction of the latter.

11. In a cup'ola. furnace, an outer sheathing, a metallic member forming a portion of the furnace liner and formed of a plurality of segments arranged adjacent each other, retaining means with which the side edges of adjacent segments are engaged to maintain the latter in assembled position,

resilient means for maintaining the retaining means in engagemet with the segments, and means for adjusting the tension of the retaining means with respect to the segments.

In Witness whereof I have hereunto set my hand.

FREDERICK A. STEVENSON. 

